The Bloom Box is the latest energy miracle that sounds too good to be true: Debuting with a wide-eyed segment on 60 Minutes, it promises to be clean, cheap and backyard-friendly, the solution to our energy problems. What is it?

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The heart of the box is a fuel cell. Though Bloom Energy's CEO K.R. Sridhar—a former NASA scientist—says it's a new kind of fuel cell. And though it's cleaner than any combustion engine out there, it still relies on fossil fuels and biofuels—not just hydrogen, like some other kinds of fuel cells do. Nevertheless, the folks at Bloom are doing something that could help make reduced emissions a reality for big businesses first, and then later, for homes.

To get a good grip on why we should care about this thing, let's first look at the basics of fuel cell technology.

Fuel Cell Basics

Like a battery, a fuel cell is an electrochemical cell, basically meaning it derives electricity from chemical reactions. Sandwiched between two electrodes—an anode and a cathode—is an ion-conducting material called an electrolyte. Fuel flows in one side, over the anode. An oxidant flows into the other side, over the cathode. What happens, very basically, is that the fuel and the oxidant react, like strangers locking eyes across a room. The metaphorical sparks that fly from that encounter are actual electrons, which flow into the fuel cell's circuit. Bingo, electricity. As with any molecular reaction, the recombination of atoms produces some waste as well—like water or carbon dioxide. So while it's cleaner, there's definitely a byproduct.

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To be clear, a fuel cell's not like a battery; it's like a power plant. Once it converts fuel to energy, it sends that energy out the door. And as such, it requires some peripheral way to physically storing the fuel ingredients, and some way to capture produced electricity—such as a battery.

There are a several different kinds of fuel cells—unsurprisingly, since they were invented in the 1830s. Generally, they are categorized based on what their electrolyte is made out of, but sometimes they're referred to by their fuel and oxidant, which varies too. You're probably most familiar with "hydrogen fuel cells," like for cars and small electronics. These are in fact proton exchange membrane fuel cells, which happen to use hydrogen as a fuel and oxygen as an oxidant. (The PEM fuel cell is what is specifically diagrammed above.)

Solid Oxide Fuel Cells

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Bloom Energy's Energy Servers are of the solid oxide variety of fuel cell. There's two ways to do up an SOFC: A tubular design, which you can see above, or a planar design, which is what Bloom uses, as you can see below, since it allows them to be stacked into very neat boxes.

The major thing about an SOFC versus other fuel cells is that the material composition means they can run crazy hot—up to 1800ºF, says the US Department of Energy—and have to, since the ceramic materials don't become active until they reach a certain temperature. Only at this temperature can they perform the chemical reactions with the fuel and oxidant we talked about above. The problem with the high operating temperatures is that traditionally it has lead to higher maintenance costs. You know, stuff breaks down. The goal for this technology is to have an "uptime" of 99.99%, as cited by cited by Scott Samuelsen, who's the director of the National Fuel Cell Research Center at the University of California-Irvine. Bloom's own trial at Google cites a 98% uptime.

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The types of fuel cells you hear more about—the "methanol" ones that can already power laptops—do their business at a much lower temperature. Toshiba has one that typically runs at 120º to 200ºF. Though Bloom's is obviously not a tech that could be a laptop's power source, the Bloom Box's higher operating temperature is a big advantage over "legacy" fuel cell technology. Bloom Energy VP of Marketing and Products Stu Aaron told me it gives them "fuel flexibility." They can use biogases from land waste or fossil fuels like propane—so far in demos it's been an even split between biogases and natural gas—whereas low-temp fuel cells require hydrogen in a much purer state that has to basically be refined or extracted via chemical processes.

While some other SOFCs use the hot exhaust generated by the reaction kind of like a cogen—a means of capturing heat emitted by a power generator, so that it too can be converted to electricity—Bloom's Energy Servers simply recycle the heat within the cell, since the temperature generated by the reaction is almost exactly the heat needed for the reaction to happen. The rated efficiency spec for their current energy server is greater than 50%, compared to around 10% to 15% for solar (though University of Delaware-led researchers did recently hit a world's record of 42.8% for solar).

Again, to be clear, the energy generated isn't emission-free: These servers generate a small amount of CO2 when converting natural gas or bio-gas. It is less than what would get released if the same fuel was combusted, however. Customers can pick which of the two kinds of fuel they'd like to use; the trade off is between "optimizing for cost or carbon reduction," depending on the company's priorities, says Aaron.

Electricity In Bloom

Right now, the only box that Bloom is selling is a 100-kilowatt-hour energy server, which you can check out there. Inside are thousands of solid oxide fuel cells—each one able to power a light bulb. The cells are arranged in stacks, which are aggregated into modules, and so on, with a common fuel input. Right now, they're just for corporations—like Google and Coca-Cola—and run about $700,000 to $800,000 each. The goal's to get them down to three grand, where they'd be suitable for home use. That may still sound expensive, but they pay for themselves in 3-5 years, says Aaron, with an energy cost of 8-9 cents per kW hour vs. the 13-14 cents it typically costs in California. (It saved eBay $100,000 on their power bill.)

But cost is where the real skepticism comes in. Fuel cells aren't a voodoo technology. They work. They produce energy. What analysts, and others, are wondering is whether Bloom's really cracked the secret to making them cheap, at least some day. The critic that CBS trotted out on 60 Minutes, Green Tech Media's Michael Kanellos, says that while there's a 20 percent chance we'll have a fuel cell box in our basements in 10 years, but "it's going to say GE." Which is fine with me, actually, because that means another season of 30 Rock jokes.

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